Processes for the production of polyhydantoin plastics by reaction of glycine ester derivatives and polyisocyanates are already known (for example U.S. Pat. No. 3,397,253).
This procedure has since undergone numerous modifications in which the polymers containing hydantoin groups are varied by addition or incorporation of other functional groups, such as amide, imide or ester groups. Many different solvents have been recommended in this regard. Hitherto, however, polymers containing hydantoin groups with the best property level have only been obtained where phenolic solvents, such as phenol, cresols or xylenols, have been used either individually or in admixture.
However, the use of phenolic solvents is accompanied by environmental pollution, so that, where polyhydantoins are applied, for example as wire enamels, from such phenolic solvents, expensive recovery systems are required for the quantitative recovery of these solvents or for their quantitative removal from wastewater and waste air.
DE-OS 28 54 383 describes a process for the production of modified hydantoins in lactones as the reaction medium. However, the polymers obtained on the one hand are yellow in color through secondary reactions and, on the other hand, have a low molecular weight which is reflected in their low relative viscosity.
Wherever polyhydantoins are used as plastics, the phenolic reaction medium has to be quantitatively removed by expensive precipitation and/or extraction processes.